To clarify, since it's kind of a confusing issue: when a Druid activates Unending Resolve gained through Symbiosis, they should be immune to all Interrupt effects, but not Silence effects. That's different from the Warlock version of the spell, which grants immunity to both.

The issue we're potentially seeing here is that the Interrupt portion of spells that also have Silence effects attached (such as Counterspell) is still going through, which is unintended. Silences will still interrupt casting, but the Druid should only have to wait for the Silence effect to wear off, and never be affected by the spell lockout from the Interrupt effect. That's the issue we're currently investigating.